[RESOLVED] Un-Subclass a Form

I am subclassing a form in my project for certain reasons. I now have the need to give the ability to unsubclass it. Mostly for reducing used resources.

I have the usual subclassing start procedure....

vb Code:

Public Sub SubClassHwnd(ByVal hWnd As Long)
    'START SUBCLASSING
    mlPrevWndProc = SetWindowLong(hWnd, GWL_WNDPROC, AddressOf WindowProc)
End Sub

But in the WindowProc I have it unsubclassing upon the WM_DESTROY message. But I need to simulate what its doing in there but upon a button click and not the ending of the program.

vb Code:

Case WM_DESTROY
            'REMOVE SUBCLASSING WHEN FORM IS DESTROYED (FORM1 UNLOADED)
            WindowProc = CallWindowProc(mlPrevWndProc, hWnd, Msg, wParam, lParam)
            UnSubClassHwnd Form1.hWnd
            Exit Function

vb Code:

Public Sub UnSubClassHwnd(ByVal hWnd As Long)
    'END SUBCLASSING
    Call SetWindowLong(hWnd, GWL_WNDPROC, mlPrevWndProc)
End Sub

I can not just call the UnSubClassHwnd procedure upon the button click so what am i missing?

Any suggestions?

Thanks

why can't you just call it in button click?

I tried that already and it would crash the ide.

UnSubClassHwnd Form1.hWnd

Thans why I was wondering if there was something I was missing. Still trying to get over this damn cold and its not letting me think clearly. Today is the first day I have written any real code in almost a week. :(

:ehh: strange, I just threw together a quick test prj - no problems at all...

Arrrg! I had it on a menu click and toggling a checkmark. Turned out that I had the call backwards. Trying to subclass when subclassing was already in place.

I switched it and now it works. So I guess all that is needed is the SetWindowLong call to unsub it.


One more issue BM as I know you are good at APIs,...


What message would I need to trap to determine the windowstate changing? I am currently using the WM_SYSCOMMAND message and checking the wParam for the SC_MINIMIZE, SC_MAXIMIZE or SC_RESTORE. Currently it works but the restore doesnt do all I need. When the Form1 is restored from min/max I need to have a second form move too.

Here is the meat of my windproc message that are being handled. The second form is supossed to move to the first forms edge upon the restore but it doesnt. Only when I resize of move the first form will it move. If I add code to resize form2 in the restore case then it sizes to the form1 Max'ed state.

vb Code:

Case WM_SYSCOMMAND
    'CATCH THE MIN/MAX/RESTORE MESSAGE
    Select Case wParam
        Case SC_MINIMIZE
            Form2.WindowState = vbMinimized
        Case SC_MAXIMIZE
            Form2.WindowState = vbMinimized
        Case SC_RESTORE
            Form2.WindowState = vbNormal
            'IS NOT SIZING CORRECTLY
            Form2.Move Form1.Left + Form1.Width + GetBorder, Form1.Top, Form2.Width, Form1.Height
    End Select
Case WM_MOVING
    'CATCH THE MOVING MESSAGE
    Form2.Move Form1.Left + Form1.Width + GetBorder, Form1.Top
Case WM_SIZING
    'RESIZE THE SECONDARY FORM SO ITS THE SAME HEIGHT AS THE MAIN FORM
    Form2.Move Form1.Left + Form1.Width + GetBorder, Form1.Top, Form2.Width, Form1.Height

the WM_SYSCOMMAND is processed before form is resized.

possible workaround (no guarantees it's the best). add a module level boolean, and catch the WM_WINDOWPOSCHANGED message:

Code:

---

    Select Case Msg
        Case WM_SYSCOMMAND
            Select Case wParam
                Case SC_MAXIMIZE
                    'Debug.Print "Maximize"
                Case SC_MINIMIZE
                    'Debug.Print "Minimize"
                Case SC_RESTORE
                    bBool = True
            End Select
        Case WM_WINDOWPOSCHANGED
            If bBool Then
                ' Position Form2
                bBool = False
            End If
    End Select

---

I seen that message too but I think it would conflict with WM_MOVING or are the two unrelated? Whats the dif between moving and positionchecged? Sounds like they both do the same thing?

only WM_WINDOWPOSCHANGED will occur when the form is restored / min / max.

both WM_MOVING and WM_WINDOWPOSCHANGED will occur if the form is moved - however, since we're only using WM_WINDOWPOSCHANGED when the bBool flag is set, Form2 won't be positioned twice

Ok, let me try it, but if they both occur when the form is moved thenshouldnt it be best to use only WM_WINDOWPOSCHANGED?

Nope, not working. Can I give a more descriptive error message. :D


Error 384 form cant be sized while its minimized. I tried without the bBool but got that message. With bBool the forms dont align up.

The remarks about the wm_positionchanged message states ...

Quote:

---

The WM_SIZE and WM_MOVE messages are not sent if an application handles the WM_WINDOWPOSCHANGED message without calling DefWindowProc. It is more efficient to perform any move or size change processing during the WM_WINDOWPOSCHANGED message without calling DefWindowProc.

---

http://msdn2.microsoft.com/en-us/library/aa923171.aspx

So if you handle the message and change the form2's position/size then your back at square one with the original error message. :(

I don't see why that would be a problem - we don't care about the WM_SIZE or WM_MOVE messages since we're not looking for them, and we're only positioning Form2, not form1

Code:

---

    Dim wPos As WINDOWPOS
    Select Case Msg
        Case WM_SYSCOMMAND
            Select Case wParam
                Case SC_MAXIMIZE
                    Form2.WindowState = vbMaximized
                Case SC_MINIMIZE
                    Form2.WindowState = vbMinimized
                Case SC_RESTORE
                    ' set windowstate here
                    Form2.WindowState = vbNormal
                    bBool = True
            End Select
        Case WM_WINDOWPOSCHANGED
            If bBool Then
                ' or here (depending on what you're wanting)
                ' Form2.WindowState = vbNormal
                CopyMemory wPos, ByVal lParam, Len(wPos)
                Form2.Move (wPos.x + wPos.cx) * Screen.TwipsPerPixelX, wPos.y * Screen.TwipsPerPixelY
                bBool = False
            End If
    End Select

---

that works (cos i tested it this time)

Please dont kill me! :D

Its the same action as with the wm_sizing and wm_move. :(

The problem is that the second form does not re-align next to the first form.

Test: both forms are displayed next to each other (stick). Then you drag form2 away from form1, minimize or maximize, restore (form1) and when restored form2 does not re-stick to form1. Its still restores to its original position. :( If I slightly move form1 then it snaps and sticks to form1. Can I send a fake move message to duplicate the manual fix?

ok. here we go.

this is gonna be easier if we process everything through one message - WM_WINDOWPOSCHANGING - it also eliminates the slight gap that would appear if you moved the two forms around.

i've done that in the attached, couple of things for you to iron out - a) Form2 doesn't snap when first loaded, b) if you Max to Min then restore Form2 goes to Normal, Form1 goes to Max. Those will both be simple to sort.


note: it might be worth your wild checking out Karl Peterson's FormPair example

edit: the buttons on Form1 don't actually do anything

Ok finally got it working. I didnt have the boolean variable setting to false when the other window states happened. Arrrg!

Thanks for the help BM.

Super Rep'd!

Arrg. One last issue with this.

When I check the menu item to subclass it doesnt snap the other form to the main form. Still have to move the form in order to get the other form to align correctly.

just position the form manually in the check event, that's probably the way with the least hassle.

Hmm, was trying to make it as universal as possible without much code in the forms. If I was to send a WM_MOVE or a SC_RESTORE message that should do the trick but then still having to send anything would mean code in the main form and not the module.

Doh! Just had to add the form2 move code to the start subclassing procedure so when in form1 you start subclassing form2 will snap to form1.

vb Code:

Public Sub SubClassHwnd(ByVal hwnd As Long)
    'START SUBCLASSING
    mlPrevWndProc = SetWindowLong(hwnd, GWL_WNDPROC, AddressOf WindowProc)
    Form2.Move Form1.Left + Form1.Width + GetBorder, Form1.Top, Form2.Width, Form1.Height
End Sub